1. Field of the Invention
This invention relates to a lens system which is capable of continuously effecting infinity photography to high magnification proximity photography.
2. Description of the Prior Art
So-called microlenses or macrolenses are known as lenses for short distance photography, but they have been limited to dark lenses in which the fluctuation of various aberrations is great between infinity photography and short distance photography and which have a small aperture ratio. Recently, to prevent the deterioration of aberrations in short distance photography, various aberration correcting techniques such as the floating system have been proposed with very successful results, but such techniques involve a great amount of movement of the lens for short distance focusing and lack operability. Moreover, the amount of movement for focusing increases in proportion to the focal length and therefore, particularly, in order to effect high magnification short distance photography with a telephoto lens, a large movement has been necessary and the construction of the lens barrel has unavoidably been bulky.
Also, as disclosed in Japanese Laid-open Patent Application No. 38138/1973, (corresponding to U.S. Pat. No. 3,942,875 and U.S. Pat. No. 3,942,876) there is known a lens system in which the entire system comprises two groups and the positive forward group is axially moved to thereby effect high magnification short distance photography, but in this lens system, the rearward group merely has the function of correcting the aberration fluctuations at short distances and the refractive power thereof is small. Therefore, the amount of movement of the forward group has unavoidably been large, as in the case of a whole axial movement system.